<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			.box {
				/* 外面盒子：相对定位 */
				position: relative;
				width: 400px;
				height: 400px;
				border: 1px solid #ff0000;
			}

			.abs-div {
				position: absolute;
				background-color: #00ff00;
				width: 50px;
				height: 50px;
				left: 10px;
				top: 10px;
			}

			.normal-div {
				background-color: #0000ff;
				width: 50px;
				height: 50px
			}

			.abs-div2 {
				background-color: #ffff00;
				position: absolute;
				top: 10px;
				left: 10px;
				bottom: 10px;
				right: 10px;
			}
			
		</style>
	</head>
	<body>
		<div class="box">
			<div class="abs-div"></div>
			<div class="normal-div"></div>
			<div class="abs-div2"></div>
		</div>
	</body>
</html>
